Nephrology · Critical Care · Internal Medicine

Free Water Deficit in Hypernatremia calculator

Enter the published formula inputs below to calculate and interpret this score.

Clinical inputs

Body weight (kg)

Estimated total-body-water fraction (fraction)

Measured serum sodium (mmol/L)

Target serum sodium (mmol/L)

Result

Complete all required inputs to calculate the score.

Formula inputs

Body weight (kg)Accepted range: 10 to 200
Estimated total-body-water fraction (fraction)Accepted range: 0.4 to 0.7
Measured serum sodium (mmol/L)Accepted range: 120 to 200
Target serum sodium (mmol/L)Accepted range: 120 to 160

Primary source

Adrogué HJ, Madias NE. Hypernatremia. N Engl J Med. DOI: 10.1056/NEJMra070613. PMID: 18184962. Scope: free-water deficit (L) ≈ total body water × (serum sodium / desired sodium − 1) for hypernatremia; total body water estimated as weight × an appropriate water fraction. (2000)

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